This invention relates to optical networks and, particularly, to waveguides including Bragg gratings.
An optical add/drop multiplexer is an important component in most optical networks. The multiplexer pulls down the desired channels from a network branch and replaces those channels with different contents. At the same time, the multiplexer lets the other channels pass through without significant insertion loss.
Generally, the optical add/drop multiplexer uses a fiber or waveguide Bragg grating. The fiber Bragg grating drops input light at the Bragg wavelength. The characteristics of a fiber Bragg grating and, particularly, its Bragg wavelength, are fixed. In other words, a particular fiber Bragg grating is written, for example, using an ultraviolet light, to have a predetermined Bragg wavelength. As a result, a given grating may only be able to reject or drop one wavelength.
At different times, however, it may be desirable to write a grating that rejects different wavelengths. Enabling an interferometer manufacturing device to convert to writing a different Bragg wavelength may be complicated and time consuming. Substantial realignment and/or recalibration may be required in some cases.
Thus, there is a need for better ways to write a waveguide with an arbitrary Bragg wavelength.